(1) Field of the Invention
The present disclosure relates to ultrasound diagnostic apparatuses and ultrasound image processing methods. In particular, the present disclosure relates to an ultrasound diagnostic apparatus that allows for examination with reference to images acquired by an ultrasound probe based on reflected ultrasound from a subject, and images captured by an imaging device and showing how the examination was performed in the past. The present disclosure also relates to an ultrasound image processing method for the same.
(2) Description of the Related Art
An ultrasound diagnostic apparatus transmits ultrasound to the inside of the subject via an ultrasound probe (hereinafter, “probe”), and receives reflected ultrasound generated due to a difference of acoustic impedance between tissues of the subject. Furthermore, using the reception signal, the ultrasound diagnostic apparatus generates ultrasound cross-sectional images (hereinafter, “ultrasound images”) showing the structure of the inner tissues of the subject, and displays the images on a monitor display (hereinafter, “display device”). Ultrasound diagnostic apparatuses are less-invasive, and are capable of displaying the state of the inner tissues in real time in the form of ultrasound images. Therefore, ultrasound diagnostic apparatuses are commonly used for shape diagnostics of living organisms.
In ultrasound examination, ultrasound images of tissues of an examination target part of the subject are compared with ultrasound images of given healthy tissues, thereby examining whether the subject's tissues are healthy or not. By examining the ultrasound images in real time, the examiner can easily identify the body part of the subject to which the probe is applied, and can detect abnormalities in the tissues, if any.
However, when the examiner examines ultrasound images on another occasion after the acquisition of the ultrasound images, the examiner does not have direct information for identifying the body part of the subject to which the probe was applied at the time of the acquisition. This is because no detailed information such as the location of the body part and the angle of the probe applied to the body part is recorded in the ultrasound images when the ultrasound images are acquired. Due to lack of such information, the examiner would not be able to recall the normal state of the tissues to be compared with the subject's tissues. For this reason, in some cases, there have been difficulties in detecting abnormalities in the subject's tissues at a high level of accuracy. In other words, there have been difficulties in ensuring an accurate diagnosis.
In response to this problem, another ultrasound diagnostic apparatus has been proposed and used, which has the function of recording information of the observed body part and the position of the probe during the ultrasound examination, in the form of a body mark and a probe mark respectively, and displaying the marks on the screen together with the ultrasound images. This apparatus enables a person who views the ultrasound images after the ultrasound examination to accurately identify the target body part.
However, this apparatus does not automatically provide body marks or probe marks, and requires that the examiner manually inputs the marks, which necessitates a great amount of labor. For example, in the case of an examination for rheumatoid arthritis, it is proposed to evaluate forty-four finger joints in total. Thus, it is common that a large number of, and a wide variety of body parts need to be examined for a single subject, and such an examination requires a great amount of labor.
In response to this problem, Japanese Patent Publication No. 4677199 proposes an ultrasound diagnostic apparatus which has a camera that captures an image showing the positional relationship between the probe and the subject. This ultrasound diagnostic apparatus generates a composite diagnostic image from the ultrasound image and the captured image, and displays the composite diagnostic images on the screen. This apparatus enables the viewer of the ultrasound images to identify the observed body part after completion of the ultrasound examination, without manually inputting the body marks, etc.